User Rights on Internet & Applications

I have a client who have 4 users on the same workstation. 3 users have full rights to application and internet. 1 user have very limit rights such as open and edit Excel file and only send and receive email. No right to other applications and no surf on the internet. Computer is Pentium 4, 3.0GHz running Windows XP Pro SP2. This computer is running on peer to peer network.

On this workstation what is the best way to implement it?